1. Field of the Invention
The present invention relates mainly to an electromagnetic fuel injection valve to be used for a fuel supply system of an internal combustion engine, and particularly, to the promotion of atomization or suppression of spray shape variations in the spray characteristics of the fuel injection valve, and improvement in the flow rate accuracy in flow rate characteristics or suppression of the amount of change to the ambient pressure change.
2. Description of the Background Art
In recent years, while regulation of the exhaust gases of an automobile or the like has tightened, improvement in the atomization of fuel spray injected from the fuel injection valve is required. With respect to the atomization of the fuel spray, various kinds of deliberation have already been made up to this point.
For example, a fuel injection device (see JP-A-2003-336563) is suggested in which an individual guide passage is provided in every injection hole, fuel is rectified and accelerated by this guide passage and flows into a swirl chamber, and the fuel is injected as a hollow conical spray from an injection hole plate outlet while the fuel forms a swirling flow in the swirl chamber and swirls within the injection hole, thereby promoting atomization.
However, since the above fuel injection device of the above JP-A-2003-336563 has an individual guide passage for every injection hole, and is structured such that the flow rectified and accelerated by the guide passage flows into the swirl chamber, there are the following problems.
A portion of the fuel within a dead volume may be decompressed and boil, and may become a vapor-liquid two-phase flow under high-temperature negative pressure. However, reduction of the flow rate when the vapor-liquid two-phase flow passes through a narrow flow passage is large, and the fuel injection device of JP-A-2003-336563 has a flow passage configuration in which a throttle to be a guide passage from the downstream of a seat to an injection hole is provided. Therefore, there is a problem in which changes in the flow characteristics (static flow rate and dynamic flow rate) accompanying changes in the temperature, ambient pressure, etc. are increased.
Additionally, since the velocity of flow which flows into the each swirl chamber depends on the shape of the guide passage, there is a problem in that the influence that shape variations of the guide passage has on deviation of injection quantity from each injection hole is great, a high-precision shape is required as the guide passage, and the manufacturing costs increase. If the deviation of injection quantity is great, the spray shape varies, and when the fuel is injected into the engine, the amount of adhesion to each part of the engine or the distribution of an air-fuel mixture varies. Therefore, there is a possibility that an increase in the amount of exhaust gas or fluctuation of engine rotation by combustion variation is caused.
In order to make a liquid film of the fuel thin and to atomize the fuel spray, it is necessary to apply a large swirling force to the fuel within the injection hole. Additionally, in order to strengthen the swirling force within the swirl chamber it is necessary to increase the offset between an injection hole inlet portion and the fuel passage while making the swirl chamber small, and the ratio of the depth/width of the fuel passage becomes large. For this reason, there is a problem in that working of the fuel passage becomes difficult, and in a case where the fuel passage is formed by a press, the lifespan of the die becomes short and the manufacturing costs increase.
In a case where a number of injection holes are formed for further atomization of the fuel spray, the diameter of each injection hole becomes small, and the fuel passage becomes narrow accordingly. Therefore, there is a problem in that working of the fuel passage becomes difficult, and in a case where the fuel passage is formed by a press, the lifespan of the die becomes short and the manufacturing costs increase.